[unreadable] Object individuation- the ability to determine whether an object is the same object, or a different object, than experienced previously - is one of our most basic cognitive capacities. Most current research has focused on the kinds of visual features (e.g., size, shape, color, pattern) infants use to individuate objects and how this changes with time and experience. What has been left open to speculation is the extent to which infants use information from other modalities to individuate objects. In light of the fact that infants live in a multimodal world - they see, touch, taste, and listen to the objects with which they come in contact - this gap in knowledge is problematic. Without this knowledge we cannot fully understand how infants solve the individuation problem in everyday situations. The research proposed in this application will move object individuation research in a new direction, by investigating infants' capacity to use auditory information as the basis for object individuation. Looking time methods will be used with infants 4.5 to 11.5 months of age. The objective of this application is to identify the types of auditory information infants use to individuate objects. The specific aims are to (1) assess the extent to which infants' use two kinds of sounds, those produced by shaking containers filled with different substances and those produced electronically, to individuate objects and (2) identify the underlying basis for the sensitivities observed. The central hypothesis for the proposed research is that young infants will demonstrate greater sensitivity to sounds that reveal something about the physical structure of the objects making them (e.g., containers filled with different substances), than sounds that are not clearly linked to the physical properties of objects (e.g., electronic tones). The outcome of this research will be used to develop theories of object individuation that focus on how infants go about individuating objects in a complex, multimodal world. These theories eventually will be used by parents, educators, and daycare providers to create environments that are most likely to facilitate learning about the physical nature of objects in healthy and at-risk infants. [unreadable] [unreadable]